ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

The Multifunctional Vitamin A

Updated on June 19, 2013

The nutrients present in our food are basically classified into two major groups -macronutrients and micronutrients. The body requires macronutrients in large quantities for healthy functioning and micronutrients are required in small quantities or in trace amounts. Vitamins and minerals are categorized under micronutrients and play a central role in various metabolic reactions. Vitamins have been further classified into fat and water soluble vitamins. Vitamin A is a fat soluble vitamin and is a common name given to a group of retinoids. Generally vitamin A is mostly associated with vision, but apart from acting as a light-absorbing molecule in the retina, it performs multifarious functions in our body.

Functions of Vitamin A

  • Role of vitamin A in promoting normal vision –

Vitamin A is a vital component of the protein rhodopsin, present in the retina of the eye. It absorbs light and visionary signals are sent to brain making the objects around us visible. It also promotes the differentiation and functioning of other tissues of the eye like cornea and conjunctival membranes

  • Role of vitamin A in immunity –

Vitamin A stimulates and activates the cells of the immune system (WBCs) which fight with various microorganisms.

  • Vitamin A as an antioxidant –

Due to its antioxidant properties it nullifies the harmful effects of free radicals. The free radicals are produced as an outcome of normal metabolic reactions or due to exposure to radiations and they can damage healthy cells, leading to diseases like cancer.

  • Vitamin A facilitates the growth and normal functioning of different organs like kidneys heart, lungs, etc.
  • Vitamin A is involved in the remodeling of the bone, hence making it important for the general health of bones.
  • Vitamin A maintains the health of the mucous membranes which covers the interior surfaces.
  • Vitamin A keeps skin healthy and promotes tooth growth.
  • Vitamin A promotes cell growth and differentiation.

After discovering various vital functions of vitamin A, let us find out the sources of this vitamin A.

Rich Sources of Vitamin A

Vitamin A is present in two forms in human diet which are, preformed vitamin A and provitamin A carotenoids. Preformed vitamin A like retinol, retinyl esters, retinal is present in animal foods. Provitamin A carotenoids like beta-carotene, beta-cryptoxanthin are plant pigments which get converted to vitamin A in our body. Some of the rich animal sources of vitamin A are liver and fish oils. Egg and milk contain vitamin A in considerable quantities. Plant sources of vitamin A include, green leafy vegetables (spinach, broccoli), yellow or orange fruits and vegetables (carrot, mango, cantaloupe, sweet potato, papaya etc) some dry fruits (dried apricots) and tomato juice. Bright orange colored sweet potatoes are the richest source of beta-carotene. Depending upon the availability and dietary habits, one can acquire vitamin A from any of these sources.

How is vitamin A absorbed by the body?

Retinal and retinoic acid are the active forms of vitamin A and both preformed vitamin A and provitamin A gets metabolically converted into these active forms. As it is a fat soluble vitamin, it gets dissolved in fats in the presence of bile acids. Vitamin A gets absorbed along with fats, through duodenal mucosal cells of small intestines. Liver stores the excess of vitamin A in the active form of retinyl esters.

Recommended Dietary Allowances for Vitamin A

Institute of Medicine recommends men to consume 900 micrograms of retinol (equivalent to 3,000 IU) and women to consume 700 micrograms of retinol (equivalent to 2,333 IU). Deficiency of vitamin A can lead to many eye problems. As the retinyl group performs unique function of absorption of light, its deficiency leads to night blindness. However if the deficiency is unrecognized and not treated it may lead to complete blindness and xerophthalmia (drying of the conjuctive). Vitamin A deficiency also affects the absorption of lipids and impairs the bile production. Pregnant and breast feeding women should be very careful regarding the dietary intake of vitamin A as it effects the infants. In cases of acute deficiency, this vitamin is also given in the form of supplements.

Excessive consumption of this vitamin is also harmful and the upper level of intake has been suggested to be 3,000 micrograms. An excessive intake hinders the positive effects of vitamin D and increases the chances of hip fracture. Some other symptoms generally noticed during excess intake are, irritation of skin, dizziness, joint pains, headache etc.

A diet rich in fruits and vegetables and animal products can keep us away from many deficiency related problem. However in case of any health issues one should seek the advice of doctor and consume vitamin A supplements in adequate quantities.

working

This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://corp.maven.io/privacy-policy

Show Details
Necessary
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
Features
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Marketing
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Statistics
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)